Re: prepaid to use with tethering
As long as you put the SIM card in a "normal" smartphone (i.e. a phone without software modification by the provider a.k.a. "branding"), you can activate tethering.
It's none of the provider's business, with what device you use up your data package, in my opinion. They may try to "forbid" tethering in their terms, but they cannot practically prevent you from using it, as far as I know. (Unless they sell you a modified phone.)
Sunrise tries to forbid tethering for most offers (Abos/post-paid and also for the SURF package options). In the small print, when you click on "Legal notices", you find this: "Mobile Internet with a mobile rate plan or a supplementary option is limited to data connections without VoIP for a single mobile phone without the use of devices connected to it, modems or other devices with built-in modems."
No such limitations with Orange/Salt and Swisscom pre-paid cards, as far as I know.
Anyway, you can just try it out. Put the SIM card in your phone and activate tethering. Then switch on some other device (e.g. notebook, tablet) and try out if you can use the WLAN which is offered by your phone.